1. Field of the Invention
The present invention relates generally to a mechanical apparatus, and more particularly to a clamping device for clamping board materials.
2. Description of the Related Art
In the manufacturing of products of stone materials, it is often necessary to adjoin two slates by an angle of 90 degrees. An adhesive is first applied to the junctures of the board materials and then the board materials are clamped and fixed with a clamping device. After the adhesive is hardened, the board materials are fixedly adjoined with each other.
Conventionally, the slates are clamped by means of a C-shaped clamp. FIG. 1 shows a commercially available clamping device 10. The clamping device 10 has a base 12 for resting a horizontal slate 14 and an upright slate 16 thereon. The clamping device 10 further has a first clamping rod 17 and a second clamping rod 18, which are identically to each other in structure. The first and second clamping rods 17, 18 vertically pass through the base 12 and are up and down movable. Each of the clamping rods 17, 18 includes an outer tube 19 and a threaded rod 20 screwed in the outer tube 19. An outer circumference of the outer tube 19 is formed with multiple annular grooves 191. A rotary button 21 is disposed at a top end of the threaded rod 20 and a clamp head 22 is disposed at a bottom end of the threaded rod 20. The clamping device 10 further has a first engaging plate 23 and a second engaging plate 24. Each of the engaging plates 23, 24 has a fixed end, a free end and a through hole (not shown). The fixed ends of the engaging plates 23, 24 are inserted in a raised section 121 disposed on a top face of the base 12. The clamping rods 17, 18 pass through the through holes of the engaging plates 23, 24. The engaging plates 23, 24 are respectively lifted by two springs 25 to keep the free ends of the engaging plates 23, 24 upward biased. The clamping device 10 further has a cantilever 26 pivotally disposed on one side of the base 12. The cantilever 26 is slidable along a guide slot 27 for adjusting the height.
In use, taking the first engaging plate 23 and the first clamping rod 17 as an example, when the first engaging plate 23 is biased, an edge of the through hole of the first engaging plate 23 is engaged in one of the annular grooves 191 of the outer circumference of the outer tube 19. Under such circumstance, the clamping rod 17 is chucked with the engaging plate 23 and hindered from sliding upward. Then the rotary button 21 is rotated to lower the threaded rod 20 and fix the horizontal slate 14 with the clamp head 22 at the bottom end of the clamping rod 17. When the free end of the engaging plate 23 is pressed down, the outer circumference of the outer tube 19 of the clamping rod 17 is no longer chucked with the engaging plate 23. At this time, a user can move the clamping rod 17 upward to release the slate 14. Similarly, the upright slate 16 can be clamped by means of the second clamping rod 18 or released therefrom. The cantilever 26 serves to hook a top end of the upright slate 16 to keep the slate 16 upright. The slates 14, 16 are clamped with the clamping device 10, whereby the junctions of the slates 14, 16 can be adhered to each other.
The above clamping device 10 is better than a conventional C-shaped clamp, however, such clamping device 10 still has some defects that need to be overcome as follows:
First, the cantilever 26 of the clamping device 10 serves to enhance the stability of the upright slate 16. However, the cantilever 26 simply contacts with the top edge of the slate without supporting the slate in any other position.
Second, when clamping the slate, the engaging plate 23 is engaged in a most suitable annular groove 191 of the outer tube 19 of the clamping rod 17 to space the clamp head 22 from the horizontal slate 14 by a shortest gap. Then the threaded rod 20 is rotated to lower the clamp head 22 for clamping the slate 14. The second clamping rod 18 is operated in the same manner. Such process is still quite time-consuming so that the slates can be hardly quickly clamped.